Angiogenesis is a process of forming new capillaries as endothelial cells of pre-existing blood vessels decompose extracellular matrix, migrate, divide, and differentiate to form new capillaries, which does not occur except in a particular case, such as growth, reproduction, or healing wounds. However, excessive angiogenesis has been reported in diseases such as growth and metastasis of a malignant tumor, age-related macular degeneration, rheumatoid arthritis, diabetic retinopathy, psoriasis, and chronic inflammation (Cameliet and Jain, Nature, 407:249, 2000). In this regard, the treatment of angiogenesis-related ailments, particularly treating a malignant tumor, using an angiogenesis inhibitor, has been studied (WO2008153237).
Formation of blood vessel requires a complicate set of processes including growth, migration, and division of vascular endothelial cells, and formation of capillaries, and many vascular endothelial growth factors and vascular endothelial inhibition factors involved in the set of processes have been discovered. The vascular endothelial inhibition factors are activated against activity of the vascular endothelial growth factors, which are necessary in the formation of blood vessel. The vascular endothelial inhibition factors naturally existing in a body is less toxic, and thus may be used in pathological inhibition of new blood vessel formation. Therefore, many pharmaceutical products related to the pathological inhibition of new blood vessel formation are under development.
A vascular endothelial growth factor (VEGF) is a typical protein controlling formation of blood vessel. The VEGF controls new blood vessel formation from differentiation of endothelial precursor cells (angioblasts) in situ, is expressed in gestational tissue, macrophages, and hyperplastic epidermal keratinocytes during would healing, and may become a cause of tissue edema related to inflammation. According to an in situ hybridization research, it has been proved that the VEGF is highly expressed in a plurality of human tumor cell lines including glioblastoma multiforme, hemangioblastoma, central nervous system neoplasms and AIDS-related kaposi's sarcoma (WO2008153237).
The VEGF combines with a VEGF receptor 1, 2, or 3 (VEGFR1, VEGFR2, or VEGFR3) present in vascular endothelial cells, induces tyrosine phosphorylation of the VEGF receptor, and brings activation of the vascular endothelial cells, and thus consequently, the VEGF has a profound effect on the process of angiogenesis. Among them, phosphorylation of VEGFR2 serves as the most important receptor in an angiogenesis signal transduction mechanism. The VEGF is up-regulated in malignant tumor cells in which angiogenesis is involved, and the VEGF receptor is also up-regulated in tumor-infiltrating vascular endothelial cells, but expression of a VEGF and its receptor in normal cells unrelated to angiogenesis is low. Accordingly, in such normal cells, interaction between the VEGF and its receptor is blocked, and angiogenesis is inhibited, and thus tumor growth does not occur.
A high level of VEGFR2 is expressed by epidermal cells infiltrating into glioma and specifically up-regulated by VEGF produced from human glioblastoma. Since VEGFR2 transcript is almost not detected in normal cerebrovascular endothelial cells, the high level of VEGFR2 expressed in gliblastoma related epithelial cells (GAEC) indicates inducement of receptor activity during tumor formation.
Therefore, research for treating cancer by inhibiting an activity of VEGF expressed at a tumor growing area to suppress angiogenesis and thus inhibit growth of a tumor, has actively progressed. Among medications using the VEGF as a target, the most typical medication that is clinically used is Avastin™, which corresponds to a VEGF neutralizing antibody and is approved by the FDA as an anti-tumor agent.
Heat shock protein 27 which is a protein with a low molecular weight and has a charperon activity, self-aggregates to form clusters with respect to external environment factors, such as free radicals, heat, toxins, or the like, and thus has a defense ability to the external environment factors (NCBI Gene Bank Accession Number: NP—001531.1). Secretion of HSP27 with a low molecular weight (HSP27 is produced in a human, and HSP25 is produced in a rat) has been confirmed by the present inventors. Many functions of the HSP27 are known, for example, the HSP27 combines with a protein inducing apoptosis of cancer cells and increases resistance of cancer cells to radiation and anticancer drugs (Oncogene. 2005 May 26; 24(23):3715-25). However, the relationships of HSP27 with VEGF function inhibition, angiogenesis inhibition, or cancer treatment are not known.